1. Technical Field
The invention relates to grids for holding and bracing fuel rods in a nuclear fuel assembly, of the type comprising a plurality of sets of mutually intersecting plates defining cells receiving fuel rods. Such grids are used for retaining the rods at the nodal points of an array with regular meshes, square or triangular. For retaining the grids on the rods so that the latter can slide in the case of differential expansion of the rods or expansion with respect to the guide tubes on which the grids are fixed, the plates have springs which apply the rods against a fixed boss of the plate opposite that which carries the spring or against another spring. Such grids are in particular used in light water cooled and moderated reactor assemblies.
2. Prior Art
Such grids are already known using double springs distinct from the plate, formed by a U-bent strip, having two active legs situated each on one side of a plate, for bearing on the rods occupying two mutually adjacent cells separated by the plate, connected together by a loop located over the plate and joined together by welding at the base of the loop. In particular, at the present time, grids are widely used comprising double springs whose legs are joined together by welding through two windows formed in the respective plate and situated on each side of a resilient mid-portion of the legs. A description of such springs and a machine for positioning them can be found for instance in document EP-A-0,163,568.
This type of grid in general gives good results. However, consequences of failure of the weld connecting together the ends of the legs remote from the loop (which has only a limited strength due to the small surface available for welding may be damageable. Following such a break, the free ends of the legs thus loosed may come into contact with the sheaths of the rod and damage them.